Television – Two-way video and voice communication – Conferencing
Reexamination Certificate
2002-03-05
2004-04-06
Ramakrishnaiah, Melur (Department: 2643)
Television
Two-way video and voice communication
Conferencing
C348S014090, C348S014130
Reexamination Certificate
active
06717607
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a method and a system for video conferences with at least three different video conference participant stations which communicate with one another, multimedia data being transmitted via a telecommunications network, which data comprise at least participant image data and/or participant audio data, and each participant receiving the participant image data of the other participants shown at the same time visually arranged on a reproduction device, e.g. a display or a VRD (Virtual Retinal Display). The invention relates in particular to methods and systems which communicate over telecommunications networks consisting at least partially of a mobile radio network.
Known is the rapid transmission, receipt and display of video images through video and television apparatus. The pictures usually have a resolution of at least 10×6 ppi (pixels per inch) in sufficiently good color and gray scale quality. A prerequisite for the transmission of the entire picture information is a minimal bandwidth for the transmission channel of several megahertz. The costs for such systems, however, are much too high for certain applications such as video conference systems for business and private use. Using media with smaller bandwidth, such as e.g. public telecommunications networks, for the transmission of video pictures is known. The transmission rate is correspondingly low for these media, however. For special applications, such as “slow scan” video systems, such a limited bandwidth can actually be sufficient. Examples therefor are security and surveillance systems in which a high picture repetition rate or high resolution is not necessary. Such systems typically use a resolution of 128×128 pixels for the whole picture, only 16 color or gray scale values being used. Video pictures of higher quality, e.g. with 640×480 pixels (European standard: 620×576 pixels, 8 bit depth of color) and a depth of color of 64 levels, as are common for video conferences, cannot be transmitted with these systems, however. A normal video picture requires about 2 million bits of information, i.e. about 250 kbytes, for gray scale pictures. With color pictures the quantity of data rises to even 750 kbytes. The data transmission rate over public switched telephone networks (PSTN) today is typically at about 57 000 bps (bits per second—for digital data this corresponds to bauds) per line in the analog area and 64 000 bps for ISDN, whereby about 30 seconds or respectively 90 seconds are needed to transmit a complete video picture of sufficiently good quality. This is by far too slow for most video conference applications. For this reason the unprocessed digital video data are compressed with the most various data compression algorithms in order to shorten the transmission time. However very good compression and decompression algorithms with a compression rate of 1/20 to 1/50 are also insufficient for many video conference applications. Moreover compression and decompression is normally time-consuming and requires corresponding energy and calculating capacity. For instance, in the field of mobile radio, it is precisely this last factor which can be decisive. It is thereby to be taken into consideration that in the field of mobile radio, in contrast to that of PSTN networks, the connection quality that allows a maximal transmission rate is not always present. Furthermore, with transmission rates lower than the maximum possible the transmission time is multiplied correspondingly. To obtain a further data compression, there are several documents in the state of the art is which propose transmitting with high resolution only a certain detail of a captured picture while all other picture sections are transmitted with low resolution. The patent publications U.S. Pat. No. 5,703,637 and U.S. Pat. No. 4,513,317 are examples which register with an eye tracking system the movement of the eyeball or of the retina, and use this information to show only a small region of the picture with high resolution. These systems make use of the feature of the human eye which is that only a small part of the retina (called fovea) is of high resolution, while the large remaining part has low resolution. The state of the art has several drawbacks, however, inter alia the disadvantage that all participants have to use the same video standard to be able to show these pictures. It is desirable, however, for video conference systems to be independent of the video standard. Moreover the fovea has a high resolution visual angle of only 2°. This fact is corrected by the brain through a natural but unavoidable and continuous scanning movement of the eye. The result of this is that, regardless of how good the visual angle and the high resolution picture section coincide, the picture appears blurry to the user with a small sharp picture detail in the center of vision. With the present state of the art this drawback can only be corrected with great effort, if at all.
SUMMARY OF THE INVENTION
It is an object of this invention to propose a new method and system for video conferences which does not have the drawbacks described above. In particular, the participant image data of video conferences should be able to be transmitted with high compression.
This object is achieved according to the present invention through the elements of the independent claims. Further preferred embodiments follow moreover from the dependent claims and from the description.
In particular, these objects are achieved through the invention in that at least three participants communicate with one another via video conference participant stations of a video conference system, multimedia data being transmitted over a telecommunications network, which data comprise at least participant image data and/or participant audio data, and each of the participants receiving the participant image data of the other participants shown at the same time visually arranged on a reproduction device, e.g. a display, of the respective video conference participant station, in that the direction of view of the participants is registered in each case by an eye tracking system and eye tracking data comprising at least data about the direction of view are transmitted to a communications unit of the respective video conference participant station, and in that transmitted in each case with full resolution and video transmission rate over the telecommunications network to the communications unit of a video conference participation station are the participant image data of that participant whose participant image data are shown on the reproduction device of this last-mentioned video conference participant station in the momentary direction of view of the participant of this video conference participant station while the participant image data of the other participants are transmitted in reduced resolution and/or at reduced video transmission rate. The invention has the advantage that the compression, i.e. the reduction, of the participant image data is independent of the video standard used since the participant image data of a participant are transmitted either reduced or in full resolution without a complicated subdivision into sub-frames taking place therefor as in the state of the art. The individual video images of a video conference interface can thereby be maintained, for example. The simplicity of the method also brings with it a minimal use of calculation capacity, which can be especially important for mobile radio devices having limited energy reserves. The drawback of the state of the art that the scanning movement of the fovea has to be corrected (such as e.g. U.S. Pat. No. 4,513,317) is eliminated with this invention since the scanning movement in the normal case relates to the object to be discerned. The impression of a sharp focus with blurry surroundings is eliminated. The entire logistical object, e.g. the video conference participant, is sharply discerned. If the glance wanders to the next logistical unit, i.
Herrmann Beat
Lauper Eric
LandOfFree
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